I'm pretty sure there isn't when it comes to drops but what you can do is reach a higher combo count. Higehr combos grant rarer drops and springs are somewhat rare.To get a better combo, use weapons that hit multiple times like the molotov for example.But other than that you have no control about what you get. You might just end up with gold medals instead of springs. It's a bad design choice to make some helm dependant on lucky drops.

Oh, that one. I don't even know why I have that, I guess luck?I would use the baseball machine because it regulary fires at the enemy and you should get a good combo. Place it in the middle and wait until it runs out. Don't use the harpoon until the subweapon has run out, you would waste the ammunition.

I've been trying with the grenade launcher and the flame thrower (haven't bought the baseball thing yet). None of the times I've gotten full-use out of it have I gotten any springs (and scarce few drops at all!)

You could also do the final boss of that chapter and get the rocket launcher but that thing has a very long setup time. But it's good for combos and deals huge damage. It's probably the best subweapon in the game.If you don't get the helmet, I guess it wouldn't be that much of a loss.Here is what you would miss:

I'm pretty sure you can put videos on app store but many don't do it. For reasons, I guess? Wouldn't surprise me, when you have to pay extra on the app store to put up a video. It's just the sort of thing that apple likes to do.